How to inject dependencies in ConstraintValidator

Here is how you can inject dependencies in ConstraintValidator class. You can read full article about validators and constraints here.
https://drupaljournal.com/article/drupal-9/entity-field-validators-and-constraints-drupal

<?php

namespace Drupal\askhub_base\Plugin\Validation\Constraint;

use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;
use Drupal\Core\Entity\EntityTypeManagerInterface;

/**
 * Validates the UniqueId constraint.
 */
class UniqueIdConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {

  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;

  /**
   * Creates a new UniqueIdConstraintValidator instance.
   *
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager.
   */
  public function __construct(EntityTypeManagerInterface $entity_type_manager) {
    $this->entityTypeManager = $entity_type_manager;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static(
      $container->get('entity_type.manager')
    );
  }

  /**
   * {@inheritdoc}
   */
  public function validate($items, Constraint $constraint) {

    foreach ($items as $item) {
      // Next check if the value is unique.
      if (!$this->isUnique($item->value, $items)) {
        $this->context->addViolation($constraint->notUnique, ['%value' => $item->value]);
      }
    }

  }

  /**
   * Is unique?
   *
   * @param string $value
   *   Field value.
   * @param \Drupal\Core\Field\FieldItemList $items
   *   Items list.
   */
  private function isUnique($value, $items) {
    $count = 0;

    try {

      $field_name = $items->getFieldDefinition()->getName();
      $entity = $items->getEntity();
      $entity_type_id = $entity->getEntityTypeId();
      $bundle = $entity->bundle();

      // Query.
      $count = $this->entityTypeManager->getStorage($entity_type_id)
        ->getQuery()
        ->condition('type', $bundle)
        ->condition($field_name, $value)
        ->count()->execute();
    }
    catch (\Exception $e) {
      // Log error.
    }

    return !(bool) $count;
  }

}